The present invention concerns a semiconductor integrated circuit device and, more in particular, it relates to a technique effective to the application of a semiconductor integrated circuit device in which a burying material is buried in grooves formed in a non-active region, and island regions (active regions) each defined at the periphery thereof with the grooves are insulated and isolated from each other.
As a technique for insulating and isolating active regions forming devices from each other in a semiconductor integrated circuit device, there has been known, for example, a BOX (Burled Oxide Isolation) technique of burying a burying material in grooves formed in a non-active region and insulating and isolating active regions each defined at the periphery thereof with the grooves from each other as described, for example, in IEDM Tech. Dig. 384 (1981), Kei KUROSAWA, et al, "A NEW BIRD'S-BEAK FREEFIELD ISOLATION TECHNOLOGY FOR VLSI DEVICES". In the BOX technology, the burying material is buried portionwise for twice in the grooves so as to flatten the inactive and active regions.
Description will now be made simply for the process of the BOX technology.
For example, a silicon oxide film and an aluminum film are successively stacked at first on a main surface of a silicon substrate, patterning is successively applied to each of them and a first mask (silicon oxide film) is formed on a main surface of the active region of the silicon film and a second mask (aluminum film) is formed on the first mask, respectively.
Then, using the second mask as an etching mask, etching is applied to the inactive region of the silicon substrate by means of an anisotropic etching such as RIE to form grooves extended from the surface of the substrate in the direction of the depth thereof and form island regions each defined at the periphery thereof with the grooves in the active region.
Then, a silicon oxide film is formed by deposition, for example, by a plasma CVD process on the entire surface of the silicon substrate including the portions on the grooves and on the island region, and the inside of the groove is buried with the silicon oxide film (first burying material).
Then, the silicon oxide film deposited to the side wall in the groove is removed by a buffer HF solution. Subsequently, by using a lift off method, the second mask is removed and, at the same time, the silicon oxide film on the second mask is removed.
Then, a silicon oxide film is formed by deposition, for example, by a plasma CVD process on the entire surface of the substrate including the portions on the grooves and on the island regions, to bury the inside of the grooves again with the silicon oxide film (second burying material). Subsequently, a photoresist is coated on the silicon oxide film by a rotary coating method, and a baking treatment is applied to form a photoresist film. The thickness of the photoresist film is formed to a thickness substantially equal with that of the silicon oxide film.
Then, anisotropic etching such as RIE is applied to each of the photoresist film and the polycrystalline silicon film under such a condition that the etching speed is substantially equal between the photoresist film and the polycrystalline silicon film, and etching back is applied till reaching the mask 1. Thus, the burying materials (first burying material, second burying material) can be buried to the inside of the grooves of the inactive region.